Toilet refill valves typically have a valve device operated by a float, the valve device opening when the toilet is flushed, to refill the water closet. Water passing through the open valve device passes into a vertical outlet tube that carries the water to the bottom of the water closet to minimize noise. The outlet tube has an anti-siphon opening above the high water line to prevent water in the water closet from flowing backward through the valve device to the home water supply, in the event that there is a vacuum in the home water supply. It is generally desirable that no check valve or the like lie along the anti-siphon air opening, to assure reliable anti-siphon operation even with a small vacuum in the home water supply.
The presence of the air opening gives rise to considerable noise during a period of perhaps one half minute during which when the water closet is refilled after each flushing. As water passes down the outlet tube, air is drawn in through the anti-siphon opening, which mixes with the water. This flowing air creates substantial noise, with some of it generated as the air flows in through the air opening, and with perhaps even more generated as the bubbles in the water flowing down the air tube are released at the bottom of the water closet to rise to the top and "pop." A refill valve, of the type which has an outlet tube that carries water to near the bottom of a water closet and which also has an anti-siphon opening, which created minimal noise during refill of the water closet, would be of considerable value.
Another source of noise in a refill valve, is a "hammer" noise which occurs when the valve device closes, when the water closet has been refilled. Where the valve device is of a type that closes suddenly, it can produce a shock that passes upstream into the pipes leading to the refill valve. A device that minimized noise from sudden closing of the valve device, would also be of considerable value.